1. Technical Field
The invention relates to an insertion assisting device and an endoscope apparatus, and more specifically, to a medical insertion assisting device which assists an endoscope for observing the small or large intestine or the like to be inserted into the body, and a medical endoscope apparatus for observing the small or large intestine or the like through the endoscope.
2. Description of the Related Art
The deep digestive tract such as the small intestine or the large intestine is complexly bent. Therefore, if an insertion portion of an endoscope is merely pushed, the pushing force is hardly transmitted to the distal end of the insertion portion, which makes it difficult to insert the insertion portion into the deep digestive tract. Therefore, there has been proposed a method of inserting the insertion portion of the endoscope into a tubular insertion assisting device (referred to as an over-tube or a sliding tube) so as to be inserted into the body. According to this method, the insertion portion is guided by the insertion assisting device. Therefore, the insertion portion can be prevented from being unnecessarily bent or flexed, which makes it possible to insert the insertion portion to the deep portion of the digestive tract.
JP 2002-301019 A discloses an endoscope apparatus in which a balloon is provided on a distal-end portion of an insertion portion of an endoscope and another balloon is provided on a distal-end portion of an insertion assisting device. According to this endoscope apparatus, the insertion portion and/or the insertion assisting device can be fixed to the digestive tract by inflating the balloon. Further, while the balloon is repeatedly inflated and deflated, the insertion portion and the insertion assisting device are alternately inserted. Then, the insertion portion can be inserted to the deep portion of the digestive tract.
In the endoscope apparatus of JP 2002-301019 A, however, if the insertion assisting device is moved in a withdrawal direction in a state where the balloon of the insertion assisting device is inflated and is in close contact with the intestine wall, it is difficult to move the insertion assisting device smoothly. This is because the air being accumulated in the base-end side of the balloon of the insertion assisting device is compressed such that the air pressure interferes with the withdrawal operation of the insertion assisting device.
To solve such a problem, Japanese Patent No. 3804068 (corresponding to US 2005/0137457 A) discloses an insertion assisting device that includes a ventilation hole provided in a position that is closer to the base-end side than a mounting position of a balloon, the ventilation hole communicating with the outside through an air insertion duct that is different from an insertion path for an insertion portion of an endoscope. According to this insertion assisting device, if the insertion assisting device is withdrawn in a state where a second balloon is inflated, the air accumulated between the insertion assisting device and the intestine wall is discharged from the ventilation hole to the outside through the air insertion duct. Therefore, the withdrawal operation of the insertion assisting device can be smoothly performed.
In the insertion assisting device of Japanese Patent No. 3804068, however, if the section area of the air insertion duct is increased to secure ventilation, liquid such as body fluid easily enters the air insertion path. Then, the liquid may leak from the end portion of the air insertion path and may contaminate a working region. Furthermore, the liquid entering the air insertion path may flow backward into the body depending on a pressure change in the vicinity of the ventilation hole.